Smoke filters



6, 1968 c. L. BROWNE 3,396,061

SMOKE FILTERS Filed June 1, 1964 Unit 3,396,061 SMOKE FILTERS Colin L.Browne, Charlotte, N.C., assignor to Celanese Corporation, a corporationof Delaware Filed June 1, 1964, Ser. No. 371,248 13 Claims. (Cl.156-178) ABSTRACT OF THE DISCLOSURE This invention relates in general toimproved tobacco smoke filters and to methods of producing such filters.

Cellulosic tobacco smoke filters, made for example of tissue or crepepaper or of rayon (regenerated cellulose) filaments, have the advantageof high smoke removal efliciencies at acceptable pressure drops acrossthe filter. Pressure drop and smoke removal efiiciency are conventionalproperties in the tobacco smoke filter art. The method of measurementmay vary slightly from manufacturer to manufacturer but withinconsequential effect on the finally assigned values. Applicant makespressure drop and smoke removal efiiciency measurements by theprocedures set forth in US. Patent No. 3,103,220.

An example of the high smoke removal efiiciencies that may be attainedby the use of cellulosic filters are the cellulosic cigarette filtersdescribed in US. Patent No. 2,954,036. A conventional length filter tip(i.e., about 17-25 mm.) made by the process described in said patent hasa smoke removal efficiency as high as about 75% while having acommercially acceptable pressure drop of not more than about 90 mm. ofwater.

However, cellulosic filter media have the disadvantage of excessivemoisture pick-up from the smoke stream which results in unsatisfactorytaste or excessive heat and smoke dryness.

Cellulose acetate, another common tobacco smoke filter medium, does notexcessively pick up moisture and has satisfactory taste. However,cellulose acetate does not have as high a smoke removal efiiciency ascellulosics.

Commercially used are tobacco smoke filters, e.g., cigarette filtertips, which are a compromise between the high smoke removal efficiencyof coliulosics (by cellulosics is meant various forms of cellulose suchas rayon filaments and paper and not cellulose derivatives such ascellulose ethers or esters) and the pleasant taste of cellulose acetate.Such cigarette filters generally are dual component, comprising asegmented filter with the segment (component) which is at hte smokersmouth being cellulose acetate and the segment (component) which isimmediately adjacent the tobacco being a cellulosic. Either or bothcomponents may contain a flavoring agent such as menthol or an agentsuch as carbon which selectively filters from the smoke certainundesirable ingredients thereof, e.g., phenolic compounds.

A major disadvanage of dual component cigarette filter tips is that eachproduction line requires two filter rodmakers, one for the cellulosicand one for the cellulose acetate and, furthermore, there are,accordingly, additional operations such as cutting discrete component (1States Patent 3,396,061 Patented Aug. 6, 1968 lengths from two differentsources and uniting the two components and in a single wrapper.

It is an object of the present invent-ion to make tobacco smoke filterswhich combine the relatively high smoke removal efiiciency ofcellulosics and the pleasant taste of cellulose acetate but which do nothave the disadvantage of the multiple assembling operation required indual component filter tips of the usual type.

Further objects will be apparent from the following description andclaims.

In the drawings:

FIG. 1 is a schematic illustration of a method embodiment of the presentinvention.

FIG. 2 is an illustration of a product embodiment of the presentinvention.

According to the present invention, there is provided a tobacco smokefilter comprising two webs (the term web herein being used to includetows) preferably a cellulosic web and a cellulose acetate tow, condensedtogether. Preferably the cellulosic web is paper (e.g., tissue or crepepaper) because it is especially inexpensive and easy to handle. However,any other cellulosic web, such as a tow of rayon filaments, may be usedto advantage. Preferably, the cellulose acetate tow is a deregisteredtOW.

The cellulosic web may be disposed centrally relative to the celluloseacetate tow or the cellulose acetate tow may be disposed centrally ofthe cellulosic web. The flow resistances of the cellulosic and celluloseacetate filter components should be balanced so as to give the properbalance of filtration between the two media. This is to give the mostdesirable taste and required filtration appropriate to the tobacco ortobacco blend employed in the cigarette. The balance of flow between thefilter media may be adjusted by varying the relative weights of thecomponents, the cross sectional configurations of the components, thecomposition or consistency of any fluid or the composition or particlesize of any solid which may be added to either or both components forpurposes of selective smoke removal and/or flavoring and/or bonding orby varying combinations of any of the above. By way of definition, whereone filter material is centrally disposed relative to the other theformer filter material is said to constitute a core and the latterfilter material is said to constitute a sheath.

Another relative disposition of the cellulose acetate tow and cellulosicweb which is provided according to the present invention is that thecellulose acetate tow and the cellulosic web may each be substantiallyin the configuration of a helicoid with the helicoids concentric and inface-to-face relationship. In the present specification and claims, theterm helicoid denotes a three-dimensional figure having the form of aflat coil or flattened spiral.

In all of the filters of the present invention, generally it ispreferred that the cellulose acetate tow and cellulosic web beinterfacially cohered. In the absence of this feature: there often willbe lower density of filter material in the neighborhood of the boundarybetween the two different materials as compared with the balance of thefilter due to imperfect joining together of the two materials and smokewill tend to preferentially flow through the resultant spaces (this isknown as a channeling effect); furthermore, a cigarette filter tip soconstructed sometimes will be deficient in firmness sufficient toprevent excessive cross-sectional deformation of the tip when handled orwhen between the smokers lips. Channeling and/ or lack of firmness canalso be overcome by increasing the total weight of filter media used soas to cause higher internal pressure within the filter rod or tipsufficient to collapse said spaces.

The interfacial coherence may satisfactorily be attained by theapplication of adhesive at the prospective interface (i.e., to thesurfaces of either the cellulose acetate tow or the cellulosic web orboth which will comprise the interface) or by the plasticization (withplasticizer and/ or heat and/or solvent) of the cellulose acetate towand/or the cellulosic web at the surfaces which will comprise theinterface. Since by the use of the plasticization method excellentcoherence generally is not attained unless both the cellulose acetatetow and the cellulosic web are plasticized, this method is not preferredbecause the plasticization of cellulosics is difiicult of attainment andthe simultaneous plasticization of both filter materials by the sametreatment, which would be the most efficient mode of operation, is notpracticable. Thus, the use of any efifective adhesive (such as starch,polyvinyl alcohol and polyvinyl acetate emulsions or other adhesiveemulsions, suspensions, pastes, solids or fluids and the like) ispreferred, especially when applied to the surfaces of both materialswhich will comprise the interface whereby especially excellent coherenceis attained.

In order that each of the cellulose acetate and cellulosic contributesubstantially to the properties of the filter, the minor componentshould make up at least about by weight of the total weight of bothmaterials. It is preferred that the minor component be no less thanabout 30% and most preferred is a 5050 product.

As with the conventional dual component filters previously referred to,either or both filter materials may have applied thereto orincorpormated therein bonding and/or flavoring and/or selectivefiltering agents. Any known method of applying or incorporating suchagents may be employed.

Also constituting part of the present invention are improved methods ofmaking tobacco smoke filters whereby the tobacco smoke filters of thepresent invention may be made. In general, such improved methodscomprise bringing together two webs, preferably a cellulosic web and acellulose acetate tow, condensing together said two webs in the form ofa single continuous rod and dividing said continuous rod (in one ormore, preferably two, operations) into a plurality of discrete lengths,said discrete lengths comprising the improved tobacco smoke filters ofthe present invention.

More specifically, a method of the present invention comprisessimultaneously feeding to the garniture of a conventional cigarettefilter rod-maker a cellulosic web, preferably paper (e.g., tissue orcrepe paper), and a cellulose acetate tow, preferably which is crimpedand deregistered, condensing said web and said tow in said garniturethereby shaping them into a single continuous rod and dividing saidcontinuous rod into a plurality of discrete lengths, said discretelengths comprising the improved tobacco smoke filters of the presentinvention.

As previously explained, it is preferred that the cellulosic web andcellulose acetate tow be interfacially cohered. For example, a polyvinylalcohol adhesive may be padded from an aqueous emulsion onto thecellulosic web and/ or the cellulose acetate tow immediately before saidweb and said tow are brought together: thus, the web and/ or tow mayeach be passed over and in contact with a rotatable absorbent (e.g.,felt-surfaced) roll which is partially immersed in a bath of theemulsion. Or, for example, immediately before the cellulosic web andcellulose acetate tow are brought together, the cellulosic web may beplasticized by being passed through a chamber containing superheatedsteam and/or the cellulose acetate tow may be plasticized by beingsprayed with a mist of glycerol triacetate, triethyl citrate or othercommon plasticizer.

Alternatively, instead of being rendered mutually coherent immediatelybefore being brought together, the cellulosic web and cellulose acetatetow may be cohered before being fed to the condensing operation and thusbe fed from a single source and as a single composite structure (forexample, from a roll of the pre-cohered composite structure). Otherwise,the cellulosic web and cellulose acetate tow are fed from individualsources (e.g., the tow from a bale, using any conventional cigarettefilter tow withdrawal system, and the cellulosic web, viz. paper, from anon-driven, rotatable roll, using driven rolls which contact the web towithdraw it from the roll).

The filter material which it is desired to dispose centrally relative tothe other filter material is fed into the trumpet of the garniture bymeans of a truncated conical funnel guide of substantially smaller exitdiameter than the width of said filter material, which funnel guidegathers said filter material into a bundle and directs the bundle intothe center of the other filter material. When such a funnel is not usedor when the two filter materials are fed as a single compositestructure, previously described, the two filter media when passedthroughv the garniture may tend to assume a relative disposition whereineach is substantially in the configuration of a helicoid, said helicoidsbeing concentric and in face-toface relationship.

Methods of deregistering a conventionally crimped cellulose acetate toware well known and any such method may be used complementary to thepresent invention. Similarly, any conventional method of plasticizingcellulose acetate tow for the purpose of bonding the filaments of saidtow to one another may be conventionally employed before the garnitureand thus serve a dual function in the present invention by alsorendering the surface of the cellulose acetate tow adherent with respectto the surface of the cellulosic web. However, it will sometimes befound desirable to employ supplementary plasticization, as previouslydescribed, for the purpose of the present invention. Also, conventionalcigarette filter rodmaking and cigarette making and filter tippingapparatus may be used in the present invention whereby the filter isfirst formed as a continuous rod, then cut into six-filter lengths,subsequently cut into two-filter lengths, each two-filter length iswrapped in cigarette wrapper paper with a column of tobacco at each endand each of the thus formed two-cigarette products is cut at its middle,i.e., through the middle of the filter which joins the two tobaccocolumns, each of said products thereby yielding two filter tipcigarettes. In the present invention there may be used a celluloseacetate tow of lower denier than conventional cellulose acetatecigarette filter tow because the tow is supplemented by the cellulosicweb.

The drawings, in detail, are described as follows:

In FIG. 1, cellulose acetate tow 12 is fed to the nip of metering rolls11 and 11' and from said nip to trumpet 15 leading to the garniture (notillustrated) of a conventional cigarette filter rodmaker (notillustrated). Simultaneously, tissue paper 13 is metered from roll 14into trumpet 15. Since tow 12 and tissue paper 13 are fed on top of eachother, neither tow 12 nor paper 13 being bundled and directed to thecenter of the other, the resultant rod is the aforesaid double-helicoidembodiment. In ghost form there is illustrated funnel 16. If such funnelis used to gather tissue paper 13 into a bundle and direct it into thecenter of tow 12, the resultant rod is an aforesaid sheath/coreembodiment. The arrow indicates the direction of movement of paper 13and tow 12.

In FIG. 2, there is illustrated a sheath/core embodiment. Darkenedportion 22 is the tissue paper (colored paper being used forillustrative purposes) and surrounding portion 21 is cellulose acetate.Such results are attained when funnel 16 is used with trumpet 15 in theFIG. 1 embodiment.

The present invention is further described by reference to the followingexample:

EXAMPLE A hollow fil, 3.0 denier per fil, 26,200 total denierconventionally crimped cellulose acetate cigarette filter tow is openedin a profiled roll unit comprising two sets of paired rubber surfacedand threaded rolls, as described in US. Patent No. 3,032,829 and is thenplasticized with glycerol triacetate in a centrifugal plasticizerapplicator as described in commonly assigned US. patent application Ser.No. 216,894, filed Aug. 14, 1962; said tow, directed by a conventionaltrumpet, is then fed to the garniture of a conventional cigarette filterrodmaker; simultaneously, to the center of the lower surface of said towis directed a web of colored tissue paper fed from a roll of toilettissue, said web being directed by a truncated conical funnel insertedpartially into the mouth of said trumpet and having an exit openingsubstantially smaller than the width of the web and of the tow wherebythe web is transversely bunched to a width substantially smaller thanthe tow width; said tow and said bunched web are passed through thegarniture wherein said tow and said web are condensed (i.e., compressed)together into a continuous rod, therein the web comprising a core andthe tow comprising a sheath about said core. The continuous rod is cutinto 6-filter tip lengths of 102 mm. by the rodmaker and is subsequentlycut into 17 mm. single filter tip lengths. The colored paper shows thatthe paper web constitutes the core of the filter rods and tips. Theproperties of rod and tip are tabulated as follows:

Rod properties:

Length 102mm. Circumference 24.9 mm. Weight 0.889 g. Acetate 0.378 g.Paper 0.391 g. Plasticizer (glycerol triacetate triacetin) 0.050 g.compressibility 20%. Pressure drop 186 mm. of H 0. Tip properties:

Length 17 mm. Pressure drop 36 mm. of H 0. Efficiency 42.4%. Particulatedelivery 27.8 mg./cigarette.

The tip pressure drop is exceptionally low. Identical length andcircumference tips made individually of 3.2 and 4.0 denier per filhollow fil and 3.9 and 4.7 denier per fil ordinary fil cellulose acetatefilter tow would be found to have a smoke removal efiiciency of about38.0% for the rods made from the hollow fil tows and about 36.9% for therods made from the ordinary fil tows (denier per fil not being asignificant parameter) when of the same rod pressure drop as the rod ofthe present example. The smoke removal efficiency (efiiciency) of therod made by the present invention is indeed substantially higher, being42.4%. It is thus seen that, since an arithmetic plot of AP v. SRE isessentially linear, at higher tip pressure drops, such as a commerciallycommon 90 mm. of H 0 pressure drop, smoke removal efficiencies would bewell up into the %-plus or %-plus range or even higher.

With regard to the rod weight, it is to be noted that the total weightof acetate (i.e., cellulose acetate), paper (i.e., the cellulosic filtermaterial) and plasticizer is 0.819 gram. The difference between thisweight and the total rod weight is 0.070 gram. This difference isaccounted for by the fact that with a conventional cigarette filterrodmaker, as in the present example, there is used a glue lineapplicator and filter wrapper attachment. The filter wrapper attachmentcomprises means for feeding a continuous strip of paper to thegarniture, to which strip, before it reaches the garniture, there isapplied a continuous line of glue by the glue line applicator. In thegarniture, the paper strip is wrapped about the filter in a single layerexcept for a slight overlap at which the resultant wrapper is sealed byanother application of glue. The aforesaid 0.070 gram weight differenceis the weight of the filter wrapper and glue. The filter wrapper isconventionally used to help maintain the integrity of the filtermaterial in subsequent machine handling and in smoking by the consumer.The glue line application is a precaution by which the filter materialis cohered to the wrapper at least along said line thereby avoiding anypossibility that the filter material will slip out of the wrapper.

It is to be understood that the above description is merely illustrativeof the scope of the present invention "and that many variations withinthe spirit of the invention may be obvious to the average worker in theart.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. In a method of making tobacco smoke filters, the improvement whichcomprises bringing together two webs, one of said webs comprising amultiplicity of continuous synthetic filaments, condensing said webstogether thereby shaping them into a Single continuous rod having aneffective filtration cross section comprising elements of each of thewebs, and dividing said continuous rod into a plurality of discretelengths, said discrete lengths comprising said tobacco smoke filters.

2. The method defined in claim 1, wherein to at least one of said twowebs is applied a selective filtering agent.

3. The method of claim 1, wherein one of said two webs is celluloseacetate tow and the other of said two webs comprises a cellulosic.

4. The method defined in claim 3, wherein said cellulosic is paper.

5. In a method of making tobacco smoke filters, the improvement whichcomprises feeding to the garniture of a cigarette filter rodmaker afirst web of filter material and simultaneously feeding through atruncated conical funnel guide and then into said garniture a second webof filter material one of said webs comprising a multiplicity ofcontinuous synthetic filaments, said funnel guide being directed towardthe center of said first web and having an exit diameter substantiallysmaller than the width of said second web, said funnel guide therebygathering said second web into a bundle and directing it to the center.of said first web, condensing said webs in said garniture whereby saidfirst web is condensed about said bundled second web thereby forming asingle continuous rod wherein the second web comprises a core and thefirst web comprises a sheath about said core, said rod having aneffective filtration cross section comprising elements of each of thewebs, and dividing said continuous rod into a plurality of discretelengths, said discrete lengths comprising said tobacco smoke filters.

6. The method defined in claim 5, wherein said first web is celluloseacetate tow and said second web comprises a cellulosic.

7. The method defined in claim 6, wherein said cellulosic is paper.

8. In a method of making filter rods wherein an elongate web of amultiplicity of continuous synthetic filaments is fed continuously tothe garniture of a cigarette filter rodmaker and condensed into a singlecontinuous rod, the improvement which comprises feeding to saidgarniture with said synthetic filament band a continuous cellulosic webcondensing said webs together in said garniture in a cross-sectionalconfiguration whereby said cellulosic web constitutes a portion of theeffective filtration cross-section, said cellulosic web comprising atleast 10 percent by weight of said web materials.

9. The method of claim 8, wherein said cellulosic web comprises at least30 percent by weight of said web materials, and is disposed interiorlyof said synthetic filament web.

10. The method of claim 8, wherein said synthetic filaments arecellulose acetate, said cellulose web and said cellulose acetate webeach comprise equal weight proportions of said filter rods, said websare interfacially cohered, and are disposed in the configuration ofconcentric helicoids in face-to-face relationship.

11. The method defined in claim 8 wherein said web 7 and said tow arefed as an interfacially cohered composite web.

12. The method defined in claim 8 wherein said cellulosic web is paper.

13. The method defined in claim 12 wherein adhesive is applied at theprospective interface of said paper and said tow whereby during saidsubsequent condensing said paper and said tow become cohered at theirinterface.

References Cited UNITED STATES PATENTS 2,900,988 8/1959 Crawford et a1161 8 Wade 131267 Schur et a1. 161 Cobb 161 Parmele 161 Schaaf 131267Muller 156-462 Gallagher 156-178 Gallagher 156180 10 EARL M. BERGERT,Primary Examiner.

D. I. FRITSCH, Assistant Examiner.

